Query optimizer-miss with unqualified expressions, bug or feature?

[Ben Clewett]

I have noticed that an unqualified boolean expression cannot be 
optimized by MySQL to use an index in 5.6.24.

For example:

CREATE TABLE t (
  i INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  a BOOLEAN NOT NULL,
  KEY a (a)
) ENGINE=InnoDB;

This will hit key 'a':

SELECT * FROM t WHERE a = TRUE;

This will return the same results, but not use key 'a':

SELECT * FROM t WHERE a;

Is this a bug, or deliberate behaviour, or a missing feature, or perhaps 
something else?

Thanks,

Ben Clewett.




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